Hemofiltration system and method based on monitored patient parameters

ABSTRACT

A multipurpose hemofiltration system and method are disclosed for the removal of fluid and/or soluble waste from the blood of a patient. The system and method are equally applicable to adult, pediatric and neonatal patients. In one embodiment, the system continuously monitors the weight of infusate in a first reservoir and drained fluid in a second reservoir and compares those weights to corresponding predetermined computed weights. When necessary, the pumping rates of the infusate, drained fluid and blood are adjusted in order to achieve a preselected amount of fluid removal from the patient&#39;s blood in a preselected time period. Application of this system and method provide repeatable and highly precise results. Alternatively, predetermined patient parameters can be monitored and the adjustment of pumping rates may be responsive to these monitored parameters. Suitable patient parameters are arterial pressure, central venous pressure, pulmonary arterial pressure, mean arterial pressure, capillary wedge pressure, systemic vascular resistance, cardiac output, mixed venous O 2  saturation, arterial O 2  saturation, blood pressure, heart rate, patient weight, and hematocrit.

RELATED APPLICATIONS

[0001] This application is a continuation-in-part application of U.S.patent application Ser. No. 08/299,899, filed Sep. 1, 1994, which is acontinuation of patent application Ser. No. 08/062,928, filed May 17,1993, now U.S. Pat. No. 5,344,568 which issued Sep. 6, 1994, which is acontinuation of patent application Ser. No. 07/775,183, filed Oct. 11,1991, now U.S. Pat. No. 5,211,849 which issued May 18, 1993.

FIELD OF THE INVENTION

[0002] The present invention is directed to a system and method of bloodfiltration, and more particularly a continuous system and method for theregulation of the rate of filtration of fluid and/or soluble waste fromthe blood of a patient based on one or more monitored patientparameters.

BACKGROUND OF THE INVENTION

[0003] For various reasons, including illness, injury or surgery,patients may require replacement or supplementation of their naturalrenal function in order to remove excess fluid or fluids containingdissolved waste products from their blood. Several procedures known forthis purpose are dialysis, hemodialysis, hemofiltration,hemodiafiltration and ultrafiltration; another related procedure isplasmapheresis. The specific procedure employed depends upon the needsof the particular patient. For example, dialysis is used to removesoluble waste and solvent from blood; hemofiltration is used to removeplasma water from blood; hemodiafiltration is used to remove bothunwanted solute (soluble waste) and plasma water from blood;ultrafiltration is a species of hemofiltration; and plasmapheresis isused to remove blood plasma by means of a plasmapheresis filter. Becausethe replacement of renal function may affect nutrition, erythropoiesis,calcium-phosphorus balance and solvent and solute clearance from thepatient, it is imperative that there be accurate control of theprocedure utilized. The accurate control of the rate of removal ofintravascular fluid volume is also important to maintain proper fluidbalance in the patient and prevent hypotension.

[0004] Various systems have been proposed to monitor and control renalreplacement procedures. For example, U.S. Pat. No. 4,132,644 discloses adialysis system in which the weight of dialyzing liquid in a closedliquid container is indicated by a scale. After the dialyzing liquidflows through the dialyzer, the spent liquid is returned to the samecontainer and the weight is again indicated. Since the containerreceives the original dialyzing liquid plus ultrafiltrate, the amount ofultrafiltrate removed from the patient is equal to the increase in totalweight in the container. This system is not driven by a weight measuringdevice and does not offer precise control of the amount of liquids usedin the procedure.

[0005] U.S. Pat. No. 4,204,957 discloses an artificial kidney systemwhich utilizes weight measurement to control the supply of substitutefluid to a patient. In this system, the patient's blood is pumpedthrough a filter and the filtrate from the blood is discharged to ameasuring vessel associated with a weighing device. A second measuringvessel containing substitute fluid is associated with a second weighingdevice and is connected to the purified blood line. By means of a pump,the substitute fluid and the purified blood are pumped back to thepatient. The first and second weighing devices are coupled to oneanother by a measuring system in such a way that a fixed proportion ofsubstitute is supplied to the purified blood stream from the secondmeasuring vessel depending an the weight of the filtrate received in thefirst measuring vessel. This system does not utilize circulatingdialysate fluid in the blood filtration.

[0006] U.S. Pat. No. 4,767,399 discloses a system for performingcontinuous arteriovenous hemofiltration (CAVH). The disclosed systemrelies upon utilizing a volumetric pump to withdraw a desired amount offluid from the patient's blood and return a selected amount of fluidvolume to the patient.

[0007] U.S. Pat. No. 4,923,598 discloses an apparatus for hemodialysisand hemofiltration which comprises an extracorporeal blood circuitincluding a dialyzer and/or filter arrangement. The system determinesfluid withdrawal per unit time and total amount of fluid withdrawn byutilizing flow sensors in conjunction with an evaluating unit locatedupstream and downstream of the dialyzer or filter arrangement in theblood circuit.

[0008] U.S. Pat. No. 4,728,433 discloses a system for regulatingultrafiltration by differential weighing. The system includes adifferential weighing receptacle having an inlet chamber and an outletchamber which allows a fixed amount of fresh dialysate, by weight, toflow through the hemodialyzer. This system operates in a sequence ofweighing cycles during which the amount of ultrafiltrate removed fromthe blood may be calculated. Additionally, the ultrafiltration rate foreach weighing cycle may be calculated. This system provides a mechanismfor determining and regulating the amount of ultrafiltrate removed fromthe blood while delivering dialysate to the patient in alternating filland drain cycles of the inlet and outlet chambers of the differentialweighing receptacle.

[0009] The need exists for a multipurpose renal functionreplacement/supplementation system which is accurate, reliable, capableof continuous, long-term operation, and which can be used effectively onadult, pediatric and neonatal patients.

SUMMARY OF THE INVENTION

[0010] The present invention is directed to a multipurpose system andmethod for removal of fluid and/or soluble waste from the blood of apatient: ultrafiltration only, hemodiafiltration, hemodiafiltration andultrafiltration, and plasmapheresis with or without fluid replacement.The system and method of the present invention can provide reliable,long term operation (5-10 days) with a great degree of accuracy (on theorder of +-2 grams regardless of the total volume of fluid passingthrough the system). The system and method of the invention areadvantageous because of the multipurpose nature thereof, therepeatability and accuracy of the processes, and the simultaneous,continuous flow of fluids in an extracorporeal blood circuit, whilebeing equally applicable to adult, pediatric and neonatal patients.

[0011] As used herein the term “hemofiltration” is to be broadlyconstrued to include hemodialysis, hemofiltration, hemodiafiltration,ultrafiltration and plasmapheresis processes. As used herein, the term“infusate” is defined to include dialysate fluid or any otherreplacement fluids which may be supplied to the patient as a part of thehemofiltration procedures.

[0012] In a preferred embodiment, the system of the present inventionincludes a hemofilter, a blood pump for pumping blood from a patientthrough the hemofilter and back to the patient, and suitable tubing forcarrying the pumped blood to and from the patent. The system furtherincludes a first reservoir for maintaining a supply of infusate, a firstweighing means for continuously monitoring the weight of the infusateand generating weight data signals correlated to the monitored weight,and a first pump for pumping the infusate from the first reservoir tothe hemofilter or appropriate blood tubing access port. A secondreservoir receives drained fluid (e.g., spent infusate or ultrafiltrate,including the fluids and solutes removed from the blood) from thehemofilter, and a second weighing means monitors the weight of thedrained fluid and generates weight data signals correlated to themonitored weight. A second pump pumps the drained fluid from thehemofilter to the second reservoir. The system also includes acomputerized controller operably connected to the blood pump, theinfusate pump, the drain pump and the first and second weighing means.

[0013] The controller periodically, but on an ongoing basis during thetreatment, interrogates at predetermined intervals the weight datasignals that are continuously generated by the first and second weighingmeans and is designed to determine therefrom the weight of infusate anddrained fluid in the first and second reservoirs at the predeterminedintervals. The rate of fluid withdrawal from the blood is alsodetermined. The controller compares the infusate and drained fluidweights to corresponding predetermined computed weights in the memory ofthe controller, and, when necessary, the controller generates controlsignals which automatically adjust the pumping rates of the infusate anddrained fluid pumps in order to achieve a preselected amount of fluidremoval from the patient's blood. Additionally, the controller isprogrammed to operate the infusate and drained fluid pumps only when theblood pump is operating. Furthermore, the blood pump is operablyconnected to and is responsive to control signals generated by thecontroller in response to or independent of the weight data signals tovary the flow rate of the blood through the hemofilter as required toachieve the desired level of fluid removal from the blood.

[0014] In an alternative embodiment, the computer controller is, byinitial selection of the operator, interfaced with one or more of thevarious monitoring systems that are operably connected to the patient.These monitoring systems, which are well known in the art, generate andoutput data signals corresponding to the monitored patient parameters,and the computer controller receives such data signals. During thehemofiltration operation, the interfaced parameters are constantlymonitored; however, the controller only responds to specific parameterdata that corresponds to the patient parameters selected by theoperator. The patient parameters which may be monitored and interfacedwith the computer controller include the following: arterial pressure,central venous pressure, pulmonary arterial pressure, mean arterialpressure, capillary wedge pressure, systemic vascular resistance,cardiac output, O₂ saturation (mixed venous or arterial), bloodpressure, heart rate, patient weight, external infusion rates, andhematocrit. Numerous of these parameters may be monitored andcorresponding output data signals generated in known manner utilizing anindwelling intravenous or intra-arterial catheter. The remainingparameters are monitored and data signals are generated by means wellknown in the art. The operator will select one or more of the aboveparameters to interface with the controller which will thenperiodically, but on an ongoing basis during treatment, interrogate atpredetermined intervals the parameter data signals that are continuouslygenerated by the interfaced monitoring system(s). The controller thenevaluates the parameter data and in response thereto, when necessary,the controller generates control signals which automatically adjust thepumping rates of the infusate, drained fluid and blood pumps so as toachieve a preselected amount of fluid removal from the patient's blood.

[0015] It will be appreciated that the system of the present inventionmay utilize a combination of monitoring and responding to the infusateand drained fluid weight data signals, as described in connection withthe first embodiment hereinabove, along with one or more of the otherpatient parameters interfaced to the controller.

[0016] By way of specific examples, in connection with monitoring thepatient's weight, the computer controller may be interfaced with a bedscale which provides continuous values for the patient's weight. Inresponse to the overall patient weight data signals, the computercontroller may control the infusate and/or drained fluid pumps toachieve a predesigned protocol for decreasing or increasing thepatient's weight over time. The change in patient's weight (by increaseor decrease) can be accomplished in either a linear or non-linear (suchas curvilinear) manner with respect to time by appropriate pump control.Similarly, the computer may be interfaced with a continuous read-outdevice of the patient's O₂ saturation and the controller will receive,evaluate and respond to the O₂ saturation data by controlling theinfusate, drained fluid and blood pumping rates accordingly.

[0017] In connection with all of the above-described monitoredparameters, the computer controller will receive data signalscorresponding and relating to each particular selected parameter from anappropriate signal generating device or source operably connected to thepatient. The controller will then, after periodic interrogation, comparethe interrogated values with predetermined desired values and willautomatically make the appropriate, predetermined changes in theinfusate, drained fluid and blood pumping rates in response to themonitored signals. Furthermore, more than one of the above-referencedparameters can be continuously monitored simultaneously and the computermay be programmed with a hierarchy to consider one or more specificparameters rather than others and will respond with the appropriate anddesired adjustments in infusate, drained fluid and blood pumping ratesbased on those selected parameters.

[0018] The computer controller is designed and programmed to adjust thepumping rates (pump speed) of the infusate, drained fluid and bloodpumps so as to provide a linear response or a non-linear (curvilinear)response to the observed changes in the selected monitored parameters.In this regard, “linear” is defined to mean a fixed, non-exponentialchange, and “non-linear” or “curvilinear” means anything other thanlinear. The selection of linear versus non-linear response profile ismade by the operator of the system depending on the needs of thepatient. For example, in certain situations it may be desirable to havean initially fast fluid removal rate that decreases over time. In thatcase a curvilinear or exponential response would be utilized. In othercircumstances, consistent or constant fluid removal over time isdesired, and so a linear response profile is selected. It is furthercontemplated that at the election of the operator the computercontroller may combine linear and curvilinear response signals so as totailor the pump rates to achieve a desired response profile. Forexample, a non-linear initial response period for fast initial fluidremoval, followed by a linear response period for ongoing fluid removalat a consistent rate.

[0019] In yet another alternative embodiment, the computer controllerreceives data signals from one or more patient infusion pumps that areotherwise independent of the hemofiltration system. These infusion pumpsare used for infusion to the patient of intravenous fluids, medications,parenteral nutrition and/or blood products. By monitoring the dataoutput from the independent infusion pumps, the extraneous total fluidvolume per unit time may be ascertained. The controller will then, asrequired, change the pumping rates of the system infusate, drained fluidand blood pumps, as necessary, so as to alter the ultrafiltration rateand/or infusate fluid rate automatically in response to changes inintravenous fluid therapy. This facilitates independent patientmanagement while hemofiltration is being performed. Proper coordinationof the controller with the independent infusion pumps allows the desiredor targeted fluid removal goals by hemofiltration to be achievedautomatically in concordance with ongoing intravenous fluid therapy.

[0020] In a preferred embodiment of the method of the present invention,blood from a patient is pumped through a hemofilter and a supply ofinfusate, which is maintained in a first reservoir, is pumped from thefirst reservoir through the hemofilter, countercurrent to the blood. Theweight of infusate in the first reservoir is continuously monitored anddata signals correlated to that weight are generated. Drained fluid(e.g., spent infusate) is pumped from the hemofilter and is received ina second reservoir. The weight of the drained fluid in the secondreservoir is continuously monitored and weight data signals correlatedthereto are generated. The signals correlated to the weight of infusateand drained fluid are interrogated at regular intervals (for exampleevery minute) by a system controller and are compared to correspondingpredetermined computed weights in the memory of the controller. Thecontroller determines the amount and rate of fluid withdrawal from thepatient's blood. If those values differ from preselected, preprogrammeddesired values, the controller generates control signals whichindependently adjust the pumping rates of the infusate and drained fluidpumps so as to achieve the desired amount of fluid removal. The controlsignals may also control the blood pumping rate.

[0021] In an alternative embodiment of the method of the presentinvention, independent of or in addition to the infusate and drainedfluid weight monitoring and pump control, the computer controller may beinterfaced with one or more of the previously discussed monitoringsystems. In this embodiment, the controller will receive, evaluate andrespond to the selected patient parameter data by generatingappropriate, responsive control signals by which the infusate, drainedfluid and blood pumping rates are controlled to achieve the desiredamount of fluid removal. This may be accomplished in combination with orindependent of the infusate and drained fluid weight monitoring.

[0022] The advantages of the system and method of the present inventionare achieved at least in part due to the continuous monitoring andperiodic interrogation of the fluid weights, and other selected patientparameters, and the adjustment of fluid pumping rates in responsethereto, including the blood pumping rate, so as to achieve ideal ornearly ideal fluid removal and replacement if necessary from a patient'sblood. Further features and advantages of the system and apparatus ofthe present invention will become apparent with reference to the Figureand the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWING

[0023]FIG. 1 is a diagrammatic representation of one embodiment of thesystem of the present invention; a variation is shown in phantom.

[0024]FIG. 2 is a diagrammatic representation of an alternativeembodiment of the system of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0025]FIG. 1 shows a diagrammatic representation of a preferredembodiment of the system of the present invention. The portion of FIG. 1shown in phantom represents an alternative embodiment of the presentinvention which will be described hereinbelow. Hemofiltration system 10is operated and controlled by a suitable controller designated generallyas 12. Controller 12 may be a programmable computer such as a COMPAQ386/S having a display 13 and is operably connected to variouscomponents of hemofiltration system 10, as will be described in greaterdetail hereinafter.

[0026] In operation, blood is pumped from a patient (not shown), whichmay be an adult, pediatric or neonatal patient, through a suitablecatheter (not shown) and input tubing 14 by means of a blood pump 16.Blood pump 16, which is preferably of the roller type, is operablyconnected to controller 12 by line 18. One suitable blood pump is theRS-7800 Minipump manufactured by Renal Systems, Minneapolis, Minn. Inputtubing 14 through which the patient's blood is pumped preferablyincludes a pressure transducer 20 upstream of pump 16. Pressuretransducer 20 is operably connected to controller 12 via line 21. Meansare included downstream of blood pump 16 for accessing input tubing 14to enable the injection or infusion of desired fluids, includingmedications and anticlotting compounds such as heparin, into thepatient's blood. The injection or infusion of such fluids to the bloodmay be accomplished in any suitable manner; FIG. 1 showsdiagrammatically a syringe and tube arrangement 22, but it will beappreciated that other means could be employed for the same purpose.

[0027] The patient's blood is pumped through hemofilter 24 by blood pump16. Filters of the type suitable for use in the system of the presentinvention are readily available; one example of a suitable hemofilter isthe Diafilter manufactured by AMICON, Denvers, Mass. Where the presentsystem is used to perform plasmapheresis, a suitable plasmapheresisfilter such as the Plasmaflo manufactured by Parker Hannifin, Irvine,Calif. can be employed.

[0028] Input tubing 14 includes a second pressure transducer 26 slightlyupstream of hemofilter 24. Pressure transducer 26 is operably connectedto controller 12 via line 28. The patient's blood exits hemofilter 24,passes through output tubing 30 and is returned to the patient via anysuitable means such as a venous catheter arrangement (not shown). Outputtubing 30 preferably includes a suitable blood flow detector 31 whichverifies that there is blood flow in the system and an air bubble/foamcontrol device such as air bubble clamp 32 to prevent the passage of airbubbles to the patient. Blood flow detector 31 and air bubble clamp 32may be operably connected (not shown) to controller 12 or directly tothe pumps to interlock all pumps upon detection of any air bubbles inthe blood or upon the cessation of blood flow. A suitable foam-bubbledetector is the RS-3220A manufactured by Renal Systems. Output tubing 30also preferably includes a pressure transducer 34 immediately downstreamof hemofilter 24. Pressure transducer 34 is operably connected tocontroller 12 via line 36.

[0029] A first reservoir 50 maintains a supply of suitable dialysate orother fluid, referred to herein generally as infusate 52. Theinfusate-containing reservoir 50 is supported by a weighing device suchas electronic scale 54 which is operably connected to controller 12 vialine 56. Infusate 52 is pumped from reservoir 50 via tubing 58 by meansof infusate pump 60, which is preferably of the roller variety. Asuitable pump for this purpose is a 31/2″ Roller Pump manufactured byPEMCO, Cleveland, Ohio. Infusate pump 60 is operably connected tocontroller 12 via line 62 and pumps infusate 52 through hemofilter 24countercurrent to the blood pumped therethrough. In accordance withknown principles, infusate 52 may extract certain components (fluidsand/or soluble waste) from the blood passing through hemofilter 24. Thefluid drained from hemofilter 24 includes spent infusate and thecomponents removed from the blood, which are referred to herein asdrained fluid 76. In an alternative embodiment wherein system 10 is usedas a fluid or plasma replacement system, e.g., to performplasmapheresis, the infusate (which may be blood plasma) from reservoir50 is pumped via tubing 59 (shown in phantom) to blood output tubing 30,thereby replacing the fluid volume removed from the blood. In thisembodiment, the drained fluid 76 from hemofilter or plasmapheresisfilter 24 does not include any spent infusate since the infusate ispumped directly to blood output tubing 30 and supplied to the patient.

[0030] The drained fluid 76 is pumped from hemofilter 24 through outlettubing 64 by means of drain pump 66, which is preferably a roller-typepump, and may be the same as infusate pump 60. Drain pump 66 is operablyconnected to controller 12 via line 68. Output tubing 64 preferablyincludes a pressure transducer 70 downstream of hemofilter 24, butupstream of drain pump 66. Pressure transducer 70 is operably connectedto controller 12 via line 72. Output tubing 64 also preferably includesa blood leak detector 67 which detects the presence of blood in thedrained fluid 76, as may occur if hemofilter 24 ruptures. A suitableblood leak detector is sold by COBE, Lakewood, Colo. as model 500247000.Blood leak detector 67 may be operably connected (not shown) tocontroller 12 or directly to the pumps to interlock all pumps upon thedetection of blood in the drained fluid. Drained fluid 76 pumped fromhemofilter 24 is pumped into a second reservoir 74 which collects thedrained fluid. Second reservoir 74 is supported by a weighing devicesuch as electronic scale 78, which is operably connected to controller12 via line 80.

[0031] Scales 54 and 78, which may be model 140 CP sold by SETRA ofActon, Me. continuously generate weight data signals correlated to theweight of infusate and drained fluid contained in reservoirs 50 and 74,respectively. Those weight data signals are continuously fed tocontroller 12, to which the scales are linked through an RS-232interface. It will be appreciated that a single scale could be utilizedin place of the two scales whereby the weight differential betweenreservoir 50 and 74 is monitored and a corresponding data signal isgenerated. Pressure transducers 20, 26, 34 and 70 all continuouslymeasure the pressure at their respective locations in hemofiltrationsystem 10 and generate pressure data signals correlated thereto whichare fed to controller 12. A suitable type of pressure transducer ismodel number 042-904-10 sold by COBE of Lakewood, Colo. When certainpredetermined alarm or danger conditions exist in the system 10, asrepresented by the pressure data signals, the controller will eitheradjust the infusate, drained fluid, or blood pumping rate, or acombination thereof, or will shut the system down entirely.

[0032] Controller 12 is preferably a programmable computer that iscapable of sending and receiving signals from auxiliary equipmentincluding pressure transducers 20, 26, 34 and 70, first and secondscales 54 and 78, respectively, and blood pump 16, infusate pump 60, anddrain pump 66. In operation, controller 12 interrogates, at regularintervals, the weight data signals generated by first and second scales54 and 78. From these signals, controller 12 determines the weight ofinfusate and drained fluid in the first and second reservoirs 50 and 74at that point in time, and compares those weights to correspondingpredetermined computed weights which have been programmed into and arestored by controller 12. By monitoring the weight of infusate inreservoir 50 and the weight of drained fluid in reservoir 74 at regularintervals, the rate of change of those weights and the rate ofhemofiltration can be calculated by the computer portion of controller12. When the weights deviate from the predetermined computed weightsand/or the rate of hemofiltration deviates from a preselected,preprogrammed desired rate, controller 12 generates control signalswhich control or adjust the rates at which blood pump 16, infusate pump60 and drain pump 66 are operated, as necessary, to adjust thehemofiltration rate to the desired rate, or to stop the pumps whenpreselected limits have been reached. This is accomplished in acontinuous manner; i.e., continuous weight data signal generation,periodic interrogation of those weight data signals and computation ofthe required weight and/or rate information, comparison to predeterminedcomputed values and automatic adjustment of the pumping rates of thepumps, as necessary, to achieve the desired amount and/or rate ofhemofiltration.

[0033] Controller 12 is programmed so that infusate pump 60 and drainpump 66 are operated only when blood pump 16 is being operated. In thecase when ultrafiltration is being performed, the pumping rate of drainpump 66 must equal the pumping rate of infusate pump 60 plus the desiredultrafiltration rate.

[0034] Controller 12 continuously receives pressure data signals frompressure transducers 20, 26, 34 and 70 and is programmed to generatealarm signals when high and low pressure limits are exceeded at any ofthe monitored locations. Furthermore, an alarm signal is generated whenthe pressure differential across hemofilter 24 exceeds a predeterminedupper limit, as monitored specifically by pressure transducers 26, 34and 70. Additionally, controller 12 may stop the pumps when preselectedpressure limits (high or low) are exceeded, as for example may occur ifthe system tubing becomes occluded or ruptures or if pump occlusionoccurs. Finally, controller 12 may signal when the infusate level inreservoir 50 reaches a predetermined lower limit and when the drainedfluid level in reservoir 76 reaches a predetermined upper limit.Hemofiltration system 10 may also include suitable blood warmer andinfusate warmer devices (not shown) to adjust and/or maintain the bloodand infusate temperatures at desired levels. Such devices may alsogenerate alarm signals when the fluid temperatures are outside ofpreselected limits.

[0035] Display 13 offers updated display of measured and computedparameters such as pressures, pressure differentials, temperatures, flowrates and amounts of infusate, drain and ultrafiltration, and alarmconditions. Controller 12 generates both visual and audible alarms andall the pumps are interlocked to prevent operation thereof under alarmconditions. Users have the option of disabling or unabling the alarms(the audible part of the alarm and its interlock with the pumps) toperform a procedure under close supervision. A printer (not shown) isoperably connected (not shown) to controller 12 to generate a hard copyof procedural data currently displayed or stored at regular intervals,at the completion of a procedure or at any desired time.

[0036] Hemofiltration system 10 can be operated in one of two modes: 1)a manual mode wherein the pumping rates of blood pump 16, infusate pump60 and drain pump 66 are provided by controller 12 when fixed voltagesare applied; and 2) an automatic mode wherein the pumps are controlledby controller 12 when the desired hemofiltration amount or rate has beenprogrammed into the controller. The automatic mode allows the system tobe paused and later continued without losing previously measured andcomputed data.

[0037]FIG. 2 shows a diagrammatic representation of several alternativeembodiments of the system 10 of the present invention. Because of thecommonality of many of the system components in FIG. 2 vis-a-vis thesystem depicted in FIG. 1, like reference numerals are intended toindicate like components. Furthermore, the system components in FIG. 2operate in the same manner as the corresponding system components shownin FIG. 1 and described hereinabove.

[0038] The system of FIG. 2 further includes interfaces betweencontroller 12 and monitoring systems which generate parameter datasignals corresponding to selected patient parameters such as O₂saturation 100, hematocrit 110, patient blood pressure 120, patientheart rate 130 and numerous other patient parameters (designatedgenerally as 140), which other parameters may be one or more of thefollowing: arterial pressure, central venous pressure, pulmonaryarterial pressure, mean arterial pressure, capillary wedge pressure,systemic vascular resistance, cardiac output, and patient weight. Whilethe O₂ saturation sensor 100 and hematocrit sensor 110 are shown asbeing connected to the patient blood line 14, these parameters can alsobe monitored by means associated directly with the patient rather thanvia blood tubing 14. In fact, whereas venous O₂ saturation could bemeasured as indicated, arterial O₂ saturation would require the monitorto be located elsewhere. The overall patient weight parameter can bemonitored utilizing a standard patient bed scale (not shown) as is wellknown in the art.

[0039] During the hemofiltration operation, one or more of the variouspatient parameters will be monitored continuously and the controllerwill, at the selection of the operator, be responsive to selectedparameter data supplied to the controller. The parameter data may beevaluated and responded to by the controller independent of the infusateand drained fluid weight data signals; i.e., the system may operate andrespond based on one or more of the selected parameters and not theweight data signals; or the system may respond to a combination of theweight data signals and one or more selected specific parameters.

[0040] One or more independent patient infusion pumps 150 may beinterfaced with computer controller 12 to supply data signals correlatedto the infusion to the patient of intravenous fluids, medications,parenteral nutrition and/or blood products. The controller 12 mayevaluate this data and make modifications to the infusate, drained fluidand blood pumping rates so as to compensate for the extraneous fluidbeing delivered to the patient by means of the infusion pumps. In thisregard, the overall fluid balance in the patient can be managedconcurrent with a hemofiltration operation.

[0041] It will be appreciated by persons skilled in the art that variousmodifications can be made to the systems and methods of the presentinvention without departing from the scope thereof which is defined bythe appended claims.

What is claimed is:
 1. Continuous hemofiltration system for removal offluid from the blood of a patient, comprising: a hemofilter; a firstpump for pumping blood from a patient through said hemofilter and backto he patient; a first reservoir for maintaining a supply of infusate; afirst scale for monitoring the weight of the infusate and generatingweight data signals correlated thereto; a second pump for pumping theinfusate from said first reservoir to said hemofilter; a secondreservoir for receiving drained fluid from said hemofilter; a secondscale for monitoring the weight of the drained fluid and generatingweight data signals correlated thereto; a third pump for pumping thedrained fluid from said hemofilter to said second reservoir; at leastone monitor for monitoring a predetermined patient parameter andgenerating parameter data signals correlated thereto; and a computercontroller operably connected to said blood pump and to each of saidsecond and third pumps, said first and second scales and said at leastone patient parameter monitor; said controller receiving said weightdata signals generated by said first and second scales and saidparameter data signals generated by said at least one parameter monitor,determining from said weight data signals the weight of infusate anddrained fluid in said first and second reservoirs, respectively, atregular intervals comparing those weights to corresponding predeterminedcomputed weights, determining from said parameter data signals thecorresponding patient parameter data, comparing the parameter data tocorresponding predetermined data, and generating control signals toadjust and thereby automatically adjusting the rates of pumping one ormore of the infusate, drained fluid and blood while the pumps arepumping during hemofiltration so as to remove a preselected amount offluid from the blood over a preselected time period.
 2. A hemofiltrationsystem according to claim 1 wherein said monitored patient parameter isselected from the group consisting of arterial pressure, central venouspressure, pulmonary arterial pressure, mean arterial pressure, capillarywedge pressure, systemic vascular resistance, cardiac output, mixedvenous O₂ saturation, arterial O₂ saturation, blood pressure, heartrate, patient weight, and hematocrit.
 3. A hemofiltration systemaccording to claim 1 further comprising: an interface with one or moreinfusion pumps supplying fluid to the patient, said controller receivinginfusion data signals from the one or more infusion pumps.
 4. Continuoushemofiltration system for removal of fluid from the blood of a patient,comprising: a hemofilter; a first pump for pumping blood through saidhemofilter and back to the patient; a supply of infusate; a second pumpfor pumping the infusate to said hemofilter; a receptacle for receivingdrained fluid from said hemofilter; a third pump for pumping the drainedfluid from said hemofilter to said receptacle; at least one monitor formonitoring a predetermined patient parameter and generating parameterdata signals correlated thereto; and a computer controller operablyconnected to said blood pump, said second and third pumps, and said atleast one patient parameter monitor; said controller receiving saidparameter data signals generated by said at least one parameter monitor,determining from said parameter data signals the corresponding patientparameter data, comparing the parameter data to correspondingpredetermined data, and generating control signals to adjust and therebyautomatically adjusting the rates of pumping one or more of theinfusate, drained fluid and blood while the respective pumps are pumpingduring hemofiltration so as to remove a preselected amount of fluid fromthe blood over a preselected time period.
 5. A hemofiltration systemaccording to claim 4 wherein said monitored patient parameter selectedfrom the group consisting of arterial pressure, central venous pressure,pulmonary arterial pressure, mean arterial pressure, capillary wedgepressure, systemic vascular resistance, cardiac output, mixed venous O₂saturation, arterial O₂ saturation, blood pressure, heart rate, patientweight, and hematocrit.
 6. Hemofiltration method for removal of fluidfrom the blood of a patient, comprising: pumping blood from a patientthrough a hemofilter and back to the patient; maintaining a supply ofinfusate in a first reservoir; pumping the infusate to the hemofilter;monitoring the weight of the infusate and generating weight data signalscorrelated thereto; pumping drained fluid from the hemofilter into asecond reservoir; monitoring the weight of the drained fluid andgenerating weight data signals correlated thereto; monitoring at leastone predetermined patient parameter and generating parameter datasignals correlated thereto; and controlling the pumping rates of theblood, infusate and drained fluid by means of a programmed computer,said computer being responsive to the infusate and drained fluid weightdata signals and to said parameter data signals, said computer receivingsaid weight data signals and said parameter data signals, determiningfrom said weight data signals, at regular intervals, the weight ofinfusate in the first reservoir and the weight of drained fluid in thesecond reservoir, comparing those weights to corresponding predeterminedcomputer weights, determining from said parameter data signals thecorresponding patient parameter data, comparing the parameter data tocorresponding predetermined data, and generating control signals toadjust and thereby automatically adjusting the rates of pumping one ormore of the infusate, drained fluid and blood while the respective pumpsare pumping during hemofiltration so as to remove a preselected amountof fluid from the blood.
 7. A hemofiltration method according to claim 6wherein said at least one monitored patient parameter is selected fromthe group consisting of arterial pressure, central venous pressure,pulmonary arterial pressure, mean arterial pressure, capillary wedgepressure, systemic vascular resistance, cardiac output, mixed venous O₂saturation, arterial O₂ saturation, blood pressure, heart rate, patientweight, and hematocrit.
 8. A hemofiltration method according to claim 6further comprising: interfacing said computer controller with one ormore infusion pumps supplying fluid to the patient, said computerreceiving infusion data signals from the one or more infusion pumps. 9.The hemofiltration method of claim 6 wherein said control signals adjustthe pumping rates of one or more of the infusate, drained fluid andblood pumps such that the fluid removed from the patient's blood isremoved in a linear profile over time.
 10. The hemofiltration method ofclaim 6 wherein said control signals adjust the pumping rates of one ormore of the infusate, drained fluid and blood pumps such that the fluidremoved from the patient's blood is removed in a non-linear profile overtime.
 11. Hemofiltration method for removal of fluid from the blood of apatient, comprising: pumping blood from a patient through a hemofilterand back to the patient; maintaining a supply of infusate; pumping theinfusate to the hemofilter; pumping drained fluid from the hemofilterinto a reservoir; monitoring at least one predetermined patientparameter and generating parameter data signals correlated thereto; andcontrolling the pumping rates of the blood, infusate and drained fluidby means of a programmed computer, said computer being responsive tosaid parameter data signals, said computer receiving said parameter datasignals, determining from said parameter data signals the correspondingpatient parameter data, comparing the parameter data to correspondingpredetermined data, and generating control signals to adjust and therebyautomatically adjusting the rates of pumping one or more of theinfusate, drained fluid and blood while the respective pumps are pumpingduring hemofiltration so as to remove a preselected amount of fluid fromthe blood.
 12. A hemofiltration method according to claim 11 whereinsaid at least one monitored patient parameter is selected from the groupconsisting of arterial pressure, central venous pressure, pulmonaryarterial pressure, mean arterial pressure, capillary wedge pressure,systemic vascular resistance, cardiac output, mixed venous O₂saturation, arterial O₂ saturation, blood pressure, heart rate andhematocrit.